Hydraulic power steering for vehicles with swingable axles



WITH SWINGABLE AXLES 5 Sheets-Sheet 1 Filed Sept. 28, 1950 FIG. 1

TREVOR O. DAVIDSON,

' INVENTOR.

.NWATTORNEY.

June 8, 1954 T. o. DAVIDSON 2,680,491 HYDRAULIC POWER STEERING FOR VEHICLES? WITH SWINGABLE AXLES Filed Sept. 28, 1950 5 Sheets-Sheet 2 436 I /a as /7 2? 42 4/ 1 :4 2 Z? TREVOR o. DAVIDSON,

V as INVENTOR.

BY arm/L w 5 [b A; FIGS 7 ATTORNEY.

June 8, 1954 T. o. DAVIDSON HYDRAULIC POWER STEERING FOR WITH SWINGABLE AXLES Filed Sept. 28, 1950 VEHICLES TREVOR O. DAVIDSON,

IN VEN TOR.

ATTORNEY.

June 8, 1954 T. o. DAVIDSON 2,680,491

. HYDRAULIC POWER STEERING FOR VEHICLES WITH SWINGABLE AXLES Filed Sept. 28, 1950 5 Sheets-Sheet 4 a: )I/ m/ m/ )l/ I 98 I 97 /a TREVOR O. DAVIDSON, 8 INVENTOR.

ATTORNEY.

June 8, 1954 2,680,491

T. O. DAVIDSON HYDRAULIC POWER STEERING FOR VEHICLES WITH SWINGABLE AXLES Filed Sept. 28, 1950 5 Sheets-Sheet 5 FIG.9

TREVOR O. DAVIDSON,

JNVENTOR.

ATTORNEY.

Patented June 8,

HY DRAULIG POWER STEERING FOR VEHICLES WITH SWINGABLE AXLES Trevor- 0. Davidson, Milwaukee,

Wis., assignor to BucyruseErie Company, South Milwaukee, Wis., a c rpora ion of. Del ware Application September 28, 1950, Serial No..18 7,235 11.Claims.. (Cl. 18079.2)

My invention relates to new and useful improvements in pivot control means, such as power-steering mechanisms for 'fifth-wheel-type two-wheeled tractors.

Such tractors commonly are used to pull twowheeled trailers, scrapers and the like, where the trailer or the scraperhas a fifth-wheel connection with the tractor.

Steering is accomplished by a turning movement of the tractor relative to the trailer or scraper, pivot. simple and rugged the fifth wheel serving as a The steering mechanism used should be yet sensitive to control. Al-

though the steering mechanism should not be affected by one of the tractor wheels encountering small obstacles or traveling surfaces diiferent from that encountered bythe other tractor wheel, some yielding movement is desirable to reduce shock produced by a large obstacle.

It also is necessary to prevent the tractor from swinging from side to soft ground.

side as a wheel encounters Furthermore, the steering mechanism should be compactly grouped around thefifth wheel.

And lastly, ing mechanism fails, matically be fifth wheel.

Accordingly, tion are:

simple design, with f if the power source of the steerthe tractor should autolocked against rotation about the the principal objects ofmy invenpivot control means of very ew parts, which will have great strength without undue bulk.

(22) To provide a compact power-steeringmechanism, closely grouped around the fifth wheel.

(4) To provide a power-steering mechanism which will absorb most of any large shock applied to one of the tractor wheels, and will permit the tractor to rotate of the shock.

(5) To provide a power-steering mechanism only slightly in the direction which will eliminate side-to-side swingingof the tractor due to variations in hardnessof the worked out a number which will be readily.- progresses.

of novel and useful details, evident as the description My invention consists in the novel parts, and in the combination and arrangement thereof, which are defined in the appended claims, and of which two embodiments are exemplified in the accompanying drawings, which are hereinafter particularly described and explained.

Throughout the description, the same reference number is applied to the same member or to similar members.

Referring now to it will be seen that:

Figure 1 is a side elevation, somewhat conventionalized, of a tractor-trailer combination, equipped with the first embodiment of my powersteering mechanism.

Figure 2 is an enlarged top view, partly in crosssection, of the embodiment of the steering device shown in Figure 1, taken along the line 22 of Figure 1, with the hydraulic steering controls and the control unit shown schematically.

Figure 3 is a rear cross-section view taken along line 33 of Figure 4.

Figure 4 is a side view partly in cross-section taken along line 4-4 of Figure 2.

Figure 5 is a rear cross-section view similar to Figure 3, but showing a variant of the rack shown in Figure 3.

Figure 6 is atop cross-section view of valve 3| and valve assembly 32 of the hydraulic system shown schematically in Figure 2 Figure 7 is an enlarged top cross-section view similar to Figure 2 of a second embodiment of the steering device.

Figure 8 is a side cross-section view taken along line 8-8 of Figure 7.

Figure 9 is a side cross-section view similar to Figure 8, but showing a variant of the embodiment shown in Figure 8.

Referring now to Figure 1, we see conventionalized two-Wheeled tractor l0, steered by steering wheel II and coupled to a conventional semitrailer wagon l2 through gooseneok l3. and fifth-. Wheel assembly M. The fifth-wheel assembly 54 includes a columnar member 15 fixed to gooseneck l3 and rotatable about vertical kingpin i6. Kingpin I6 is mounted on tractor it by means of bracket I! and horizontalpin I8 on the longitudinal axis of the tractor. Pin 18 is mounted in bracket I1, which is rigidly attached to tractor Either tractor I 0 or semi-trailer I2 may then the accompanying drawings,

l9 and trailer l2 in the plane of Figure l is prevented.

Housing l9, rigidly attached to kingpin l6, contains the steering device, the first embodiment of which is detailed in Figures 2 to 5 inclusive, a second embodiment being detailed in Figures '7 to 9 inclttsive, each embodiment having two variants.

Turning now to Figure 2, we see that housing |9 has a rearward extension 20 on each end of which is attached a cylinder with a closed outer end, the two cylinders being numbered 2| and 22 respectively. Contained within housing as is rack 23, at each end of which is fixed a piston, numbered 24 and 25 respectively, which pistons fit within cylinders 2| and 22.

Rack 25 meshes with spur gear 25, which is mounted within housing I9 and attached to column l5 for rotation therewith. It is obvious that rack 23 could be connected indirectly by gearing to gear 26, though I prefer the direct meshing connection shown; however my invention is not to be limited to such direct connection.

Pump 21, which is mounted on tractor Ill and powered by the engine of tractor i9, is a conventional hydraulic pump that forces hydraulic fluid through outlet line 28 into valve 28, which valve is well kown in the art and forms no part of my present invention, and so is merely shown schematically in the figures. Valve 23 controls the flow of hydraulic fluid, having three settings for diverting the fluid into any one of three channels: (1) through line 39, valve 3|, valve assembly 32, and line 33 into cylinder 2|; (2) through line 35, valve 3|, valve assembly 32, and line 35 into cylinder 22; or (3) through return line 36 back to reservoir 31. Valve 3| and valve assembly 32. will later be described in detail and their functions explained fully.

Hydraulic fluid reservoir 3? is connected to the inlet Side of pump 2? through lines 38a and 38b. Valves 29 is connected to the inlet side of pump 21 through lines 380 and 38b. One-way spring-actuated check valve 39 in line 33a prevents how of hydraulic fluid from line 3% through line 38a into reservoir 31, but permits flow from reservoir 3? through line 38a, into line 3% when there exists in line 381) a pressure suificiently lower than the gravity-created pressure in reservoir 31 to overcome the actuating spring 1 in check valve 39.

Line fiila, which leads from extension to adjacent cylinder 2| to reservoir 31, prevents bot toming of piston 25 in cylinder 22 by carrying actuating fluid from cylinder 2! back to reservoir 31 when rack 23 reaches its limit of travel to the right. Line 45b performs a similar function for movement of rack 23 to the left.

Valves 29 and 3| and valve assembly 32 may be located at any appropriate and convenient place on the tractor It or on housing it or its extension 20. Valve 29 is actuated to divert fluid into either line 30 or line 34 by steering wheel H, through conventional mechanical, hydraulic or electrical controls (not shown) as desired.

Thus Figure 2 illustrates the invention with what is known as a closed hydraulic system, in which the fluid-return line under at least some conditions leads directly to the inlet side of the pump. Such a system has certain advantages over an open hydraulic system, in which the return line leads into the reservoir and the reservoir is the only source of fluid for the pump. These advantages will be later described.

Dust cover 4| is removably attached to housing |9 by means such as cap screws 52 (Figure 4) and fits closely around but in rotatable relation with column |5.

Rack 23 is divided longitudinally in a horizontal plane into three segments, 430., @311 and M. This is better shown in Figures 3 and 4. Segments 43a and 432) are fixed to piston 25 and extend just short of piston 24. Segment M is fixed to piston 24 and extends just short of piston 25. Bands 55 are fixedly attached to segments 53c and 13b to guide segment M longitudinally between segments 43a. and 43b, for reasons which will be described later.

Figure 5 shows a variant in which rack 23' is in integral form with bleeder passage 16 drilled longitudinally therethrough and through pistons 24 and 25. The function of bleeder passage 45 will be described later.

Turning now to Figure 6, which shows valve 3! and valve assembly 32 in section, it is seen that valve 3| is made up of plunger 41, casing 48 and compression springs 49 and 56 which are of equal strength. Casing G8 has pump ports 5i and 52, and operating ports 53 and 5%. Passages 51 and 58 connect pump ports 5| and 52 to operating chambers es and so respectively. Passages 55-6l and 55-52 connect pump ports 5| and 52 to return chambers 53 and 6G. Plunger i? has annular grooved depressions t5 and 65 for return flow to passages 55 and 5G. Bleeder hole B'i, bored lengthwise through the stem of piston 4?, permits either spring 49 or 56 to return plunger 4'! to neutral position (Figure 6) when flow has ceased and a small residual fluid pressure opposes such return.

When hydraulic fluid under pressure sufficient to overcome spring is admitted through port 5|, plunger 41 will move to the right, thus uncovering port 53 so that the fluid will flow from line 36 through port 5|, passage 5?, operating chamber 59 and operating port 53. Port 54 will also be uncovered, so that a return-flow passage will be presented through port 5 3, return chamber B l, passage 56, passage 62 and port 52 to line 34. The flow through bleeder hole 8? is not sufficient to materially reduce the pressure admitted through port 5|.

If hydraulic fluid under pressure is admitted to operating port 52, the converse will occur: the pressure will overcome spring til, plunger 41 will move to the left, uncovering ports and 53, fluid will flow out of valve 3| through port 5 and a return-flow passage will be presented through port 53, return chamber 83, passage 55, passage 5! and port 5| to line Ell.

Valve assembly 32 is made up of four valves, compound valves 68 and '69 and relief valves ill and H, these four valves being shown in Figure 6 in one block, though they could be separated and joined together operatively by means of hydraulic lines.

Port 53 of valve 3| connects directly to lower chamber E2 of compound valve 68, lower chamber l2 being separated from upper chamber l3 by plunger ltd. Plunger l ia is actuated by spring 15a. Chamber 73 connects with chamber 58, which in turn connects with hydraulic line 33 through port ll. Passage am connects chamber 16 to relief valve ll.

Compound valve 68 also includes plunger 18a, which is actuated by spring ll-la, to normally block passage 8011 through plunger 14a.

Compound valve 69, similar to valve 58, is made up of lower and upper chambers 82 and 83,

- chamber 84-: and port 85.

One-way relief valve 10 operatesto relieve any excess pressure in chamber 16 that may arise when plunger 47 is in the neutral position shown is actuated by spring 89.

One-way relief valve 1| issimilar to valve 10'. It includes passage 86b, chamber 811), plunger 90 and spring 9|.

merely flows through line 28, valve 29, line 36 and back to reservoir 31. Pump 21'draws fluid from reservoir 3'! through lines 38a and 3812.

When the enters chamber 12 of compound valve 68, where the pressure, being sufficient to overcome spring 15a, forces plunger 14a to move upwardly, so that the fluid enterschamber 13, passes through chamber 76, port 11, and line 33 and enterscylinder 2|. In cylinder 2| the fluid pressure forces piston 24, carrying rack 23 with it, to the right,

thus rotating gear 26 in a counterclockwise manwith respect to rotation about a vertical axis, and gear 26 issupported by and in fixed relation to trailer l2,- there results a clockwise movement of tractor l0 relative to trailer |2 about the pivot of kingpin l6, thus changing to the right the direction of travel of the tractor-trailer unit.

This fluid passes through port 85 and enters chamber 84 (Figure-6), passages 86b and 8|b, and chambers 83 and 81a. Valve It], being a one-way valve, prevents passage of the 791) is weaker than spring 9|, so the pressure forces plunger 1% downwardly, permitting the fluid to pass through compound valve 69 into chamber 82.

Since plunger 41 by the fluid pressure entering through port port valve 3|, spring 50- in valve 3| come spring 79b, therethe face of piston 25 opposing pressure against pressure is proportional to the strength of spring 191; or 19b, asthe case may be. The opposing forces on pistons 24 and 25 This provides an automatic take-up and-prevents any looseness or play between the rack and the gear, even though there be wear of the teeth on the rack and'gear through long use,

It will be seen that rack 23 could be constructed of a number of segments different from the three I have chosen without departing from my invention.

If rack 23' be in one integral there will be no automatic take-up, but a simple relief means such as bleeder passage 46 through rack 23 and pistons 24 and 25 may be substituted for relief valves 70 and II;

When steering wheel H is turned to steer tractor Ii! to the left, valve 29 is-rotated so as to divert fluid to flow through line 34, pump port 52, passage 58, operating chamber 60, operating port 54, compound valve 69, passage 8|b, chamber 84, line 35 and into cylinder 22. Return fluid from cylinder 2| will flow through line 3 3, chamber 16, compound valve 68, operating port 53, return chamber 63, passage 55, passagefil, pump port 5|, line 30, valve 29, and line 380-381) back to the inlet side of pump 271 When steering wheel II is returned to'neutral position, valve 29 returns to neutral'setting in which fluid from pump 21 is returned to reservoir 37 through line 36, the flow of fluid into cylinder 2| ceases, and no further relative movement between tractor In and trailer- |2 occurs. Then, since there is no movement of fluid through and no consequent source of dynamic pressure in will push plunger 41 to the left into neutral position (Figure 6), the fluid displaced from operating chamber 59 of valve 3| by such return movement'of plunger 47 flowing through bleeder hole 6'! in the stem of plunger 47 into operating chamber 60. When plunger 4'! is in the neutral position, the fluid in cylinders 2| and 22 is locked therein, except as'follows:

If the lefttractor wheel hits a rock, this imposes a shock load on the steering device and tends to turn the'tractor. This results in a sudden increase in fluid pressure in cylinder 2! (Figure 2). Relief valve l0 (Figure 6) is provided to-relieve this shock. When the pressure in cylinder 2| reaches a predetermined point (the pressure in line 33, chamber 76 and passage 86a being, of course, the same), plunger 88 will spring 89, permitting fluid to flow into chamber 81a, passage 8 b, chamber 84, line 35 and into cylinder 22. Since pres- Surein cylinder 22 was decreased by the tendinto cylinder 22, swingingly drift to. theleft, thus rolling with the imposed shock load and decreasing the likelihood of damage from the shock. This drift longer overcomes spring 89.

Conversely, if the shock load imposed, ontractor In is in the opposite direction, the drift will be opposite, relief spring 5| being overcome and fluid flowing out of cylinder 22, through line 35, into chamber 84, passage 86b, chamber 81b, passage B l a, chamber H5, line 33 and into cylinder 2 I.

When rack 23' is in one integral piece (Figure 5), flow of fluid through relief means such as bleeder passage 46 relieves excess pressure in one of cylinders 2| and 22 over the pressure in the other.

The purpose of valve 3| is to hold the tractor from swinging freely if a failure occurs in the hydraulic steering system. When valve 29 is in neutral position, plunger 41, being also in neutral as shown in Figure 6, blocks any flow of fluid into or out of cylinders 2i and 22, except as permitted by relief valves 1!! or ii.

If the hydraulic system fails between pump 2'! and port 51 of valve 3| when fluid is being pumped to cylinder 2!, spring 50 will return plunger 41 to the neutral position (Figure 6), thus blocking the fluid in cylinders 2| and 22 and so preventing further relative movement between tractor 1c and trailer 12. Conversely, upon a failure between pump 3| when fluid is being pumped to cylinder 22, spring 49 will return plunger 4! to neutral position (Figure 6), again preventing further relative movement between tractor l and trailer 2.

The advantage of using a closed hydraulic system, as illustrated in Figure 2, in conjunction with valve 3| is that if the hydraulic system fails between port '52 of valve 3i and pump 21 when valve 29 is set to divert fluid to cylinder 2 l, pump 2! will be starved for fluid as soon as lines 34 and 33b-38c are emptied, because the atmospheric pressure admitted into lines 34 and 38b-38c by the failure will, when added to the force exerted by the spring of check valve 39, keep check valve 39 closed against flow from reservoir 31 to the intake of pump 2?. Thereupon the pressure at port 51 will be lost and spring 50 will force plunger 41 to the left, again blocking ports 53 and 54 and preventing relative swinging movement between tractor ill and trailer 12. Similarly, if failure occurs between port of valve 31 and pump 21 when valve 29 is set to divert fluid to cylinder 22.

Valve 3i performs an while rack 23 is moving in cylinder 22, the left wheel of tractor til strikes an obstruction which also tends to move rack 23 to the left, the pressure in cylinder 22 and in the hydraulic system between cylinder 22 and pump 21 will drop, allowing spring 49 to return plunger M to neutral position (Figure 6) and so prevent overcontrol until the obstruction has passed. Similar results obtain for steering in the other direction when the right wheel of tractor H! hits an obstruction.

A second embodiment of my invention is shown in Figures '7, 8 and 9. Spur gear 82 is keyed to column it which is fixed to gooseneck l3 of trailer 12. Housing 93, in which pinions 94 are rotatably mounted about the periphery of gear 92 by means of pins 95, is fixed to kingpin l6. Pinions 94 mesh with gear 92 and in conjunction with gear 52 form a gear-type hydraulic motor.

Chamber 93 (Figure 8) in housing 93 is connected to hydraulic line 33 through port 91. Chamber 98 in housing 93 is connected to hydraulic line 35 through port 99. Passages I00 lead through chamber 98 from chamber 96 to one of the points of intersection of'the outside circumferences of pinions 94 with the outside circumadditional function. If,

21 and port 52 of valve to the left under pressure ference of gear 92. Passages l0! lead from chamber 98 to the other points of intersection of pinions 94 and gear 92.

The second embodiment ates as follows:

When valve 29 is set to divert fluid under pressure from pump 21 through line 30, valve 3 l valve assembly 32, and line 33 into chamber 96, the fluid will go through passages 10B to the right side (Figure '7) of each of pinions 94. This will set up pressure forcing the pinions to rotate in This rotation will cause of my invention opera clockwise direction. housing 93 (and tractor Ill, to which it is fixed) to rotate in a clockwise direction with respect to gear 92 (and trailer 2, to which it is fixed) thus turning the tractor Ill to the right.

Fluid which enters through passages I08 will be carried (by the clockwise rotation of pinions 94 and the counterclockwise rotation of gear 92) around between the teeth of the pinions and the teeth of the gear to passages Hll through which it will discharge into chamber 98, then through line 35 and finally back to the intake side of pump 21 through lines 380 and 382).

To steer tractor ill to the left, valve 29 is set to divert fluid under pressure from pump 2? through line 34, valve 3|, valve assembly 32, line 35 and into chamber 98. The fluid then goes through passages l8! to the other side of pinions 94. The pressure causes the pinions to rotate in a counterclockwise direction, resulting in steering the tractor to the left. The fluid is discharged through passages into chamber 36, whence it returns to the intake side of pump 2'1.

One or several pinions may be used, the hydraulic pressure required for operation decreasing with increase in number of pinions.

Figure 9 illustrates a variant of my second embodiment, in which pinions I02 and H13 are mounted in housing N34 to mesh with gear 92 (fixed to column 15) housing H3 1 being fixed to kingpin iii. Rotation of pinions I03 is used to turn tractor ill to the right, and rotation of alternate pinions N12 is used to turn tractor ID to the left. That is, regardless of the number of pinions utilized, alternate pinions drive against gear 92 to produce steering of the tractor In in a given direction.

In this variant, adjacent pinions are paired for the purpose of fluid flow, alternate pairs of adjacent passages being connected by passages me.

In other respects, the variant of Figure 9 is similar to the embodiment shown in Figures 7 and 8, except that compound valves 68 and 59 may be utilized to eliminate backlash between the pinions (m2 and H33) and gear 92, as explained below.

The variant of my second embodiment (Figure 9) operates as follows: When valve 29 (Figure 2) is set to divert fluid under pressure into line 39, through valve 3|, valve assembly 32, line 33 and into chamber 85, the fluid will pass through passages IGG and act upon pinions 103 so as to rotate the pinions in a clockwise direction. This steers tractor ill to the right as previously explained. The fluid which entered through passages we is carried around by the teeth of pinions 163, through passages H15, around by pinions I02 and out passages l0! into chamber 98. Then the fluid passes out through line 35, valve assembly 32, valve 31, line 34, valve 29, line 380-381) and back to the intake side of pump 21.

Since the return fluid must overcome spring 1% of compound valve 69, there will be a consequent reluctance to rotation on the part of ma am '9 pinions I02, due to the fact that the discharge through passages l| can occur only as spring 7912 is overcome. Pinions I02 then act as brakes yieldably resisting the rotation of gear 92 with respect to housing I04 caused by the rotation of pinions l 03. This resistance results in a gripping of the teeth of gear 92 between the teeth of pinions I02 and I03, which eliminates backlash.

To steer tractor [0 to the left, valve 29 is set to divert flow in the direction opposite to that just described.

Whenever in my claims I refer to a gear, I mean to include all conventional types of gears, such as spur gears, bevel gears and racks, without being limited to the enumerated types.

Having now described and illustrated two embodiments of my invention, I wish itto be undermy claims.

I claim:

means and the member on said power-steering mechanism being further characterized by the fact that the hydraulic ram means comprises a pair hydraulic pressure fluid; a double-acting hydraulically-actuated power-mechanism to effect the steering of the vehicle; a reversing valve; a supply conduit extending from the source to this 10 ing-valve and the power-mechanism; and "an automatic valve intercepting both passages, to prevent loss of control versing valve and two ports connecting with the passages on the side toward the power-mechasage over that in the other passage.

3. A power-steering mechanism according to claim 2, characterized by having 5. A power-steering mechanism according to claim 4, still further characterized by having 'resure in the other passage.

7. A power-steering mechanism according to claim 2, characterized by the fact that the powerframe, to rotate relative to the A power-steering mechanism according to 9. A power-steering mechanism according to claim 8, still 10. A power-steering mechanism according to claim 2, characterized by the fact that each end of the casing constitutes a cylinder, in which one end of the plunger acts as a piston; that the ing in a portion of the casing intermediate the two cylinders; that the portion of each passage on the side toward the power-mechanism ends in a port in the casing; that the plunger has two cross-passages, and is spring-biased to assume a central position, in which it blocks flow both to and from the power-mechanism; but when pressure fluid from the reversing valve is admitted to either cylinder, the plunger slides toward the farther end of the casing, the adjacent crosspassage admits fluid from the cylinder to the adjacent port on the side toward the power-mechanism, and the farther cross-passage admits fluid from the farther port on the side toward the power-mechanism to the farther port on the side toward the reversing valve.

11. A power-steering mechanism for a vehicle, which includes a first end frame and a second end frame, each end frame having ground-engaging means, said mechanism comprising: a first member mounted upon the first end frame for oscillation about a horizontal longitudinal axis of said end frame and for rotation with the first end frame about an upstanding axis, a second member connected to the second end frame and mounted for rotation with the second end frame about said axis relative to the first member, a gear rigidly mounted on one of said members to rotate when the member on which it is mounted rotates about said axis, an hydraulically-operated toothed mechanism, with its teeth engaging said gear, movably mounted on and in constrained relation to the other member, whereby hydraulic actuation of the toothed mechanism causes the gear and the member on which it is mounted to rotate relative to the member on which the toothed mechanism is mounted; said power-steering mechanism being characterized by the fact that the hydraulically-operated toothed mechanism comprises a pair of hydraulically-actuated toothed means both said toothed means meshing with said gear, one of said toothed means being hydraulically actuable to rotate the gear in one direction, and the other of said toothed means being hydraulically actuable to rotate the gear in the opposite direction; and valve means associated with each of said toothed means to maintain hydraulic fluid pressure above a predetermined minimum against each of said toothed means to force said two toothed means in opposite directions and thereby eliminate backlash between said toothed means and said gear.

References Cited in the file of this patent UNITED STATES PATENTS 

